I remember and used Acoustic Couplers at 110 Baud, approximately 110 bps.
1200/75 Baud Down/Up was an improvement, then 300/300.
56 Kbps, running typically about 44 Kbps - WOW !!
Also in the early days of Mobile Phones, three were delivered to our company, as three separate sub-assemblies each, no instructions.
I tackled putting together the first, eventually turned out that the sub-assemblies were linked, so had to dis-assemble and re-assemble with the related parts.
Got it working on Voice, then assembled the other two.
They were also supposed to handle FAX and Dial-Up.
Eventually the supplier mentioned that these were separate numbers, so three phones, nine numbers, each needing individual registering and authorisation!
The first real use was from Portugal to Scotland, so another learning cycle.